JPH06220539A - Production of domain-refined grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To provide the method for producing a domain-refined grain-oriented silicon steel sheet excellent in magnetic properties. CONSTITUTION:As for one kind among intermediate stage domain controlling methods, at the time of producing a mirror finished material, a steel sheet after being subjected to primary annealing is provided with grooves by a roll, and the fact that, at the time of the press-sticking thereto, in the case the primarily annealed sheet stuck with oxide powder is rolled with the roll with projections, it is press-stuck and falling does not occur, is introduced from a theoretical formula. In this way, the method for producing the domain-refined grain-oriented silicon steel sheet capable of the production combining intermediate domain control and the dry coating of powder with ultralow core loss can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented silicon steel sheet having excellent magnetic properties and a method for producing the same.

[0002]

2. Description of the Related Art 1-7 excellent magnetic properties for transformers, etc.
%, When manufacturing a grain-oriented silicon steel sheet containing Si,
In the final annealing step of performing so-called secondary recrystallization, it is extremely industrially possible to obtain secondary recrystallized grains having a sharp {110} [001] orientation, commonly referred to as GOSS orientation, whose directionality is preferable for magnetic properties such as iron loss. is important.

On the other hand, there are many physical factors that control iron loss, but the size of the magnetic domain is particularly important, and it is well known that subdivision of the magnetic domain is effective in reducing iron loss. It is also known that a smoother surface makes the flow of magnetic flux smoother, which is also effective in reducing iron loss. For this reason, in the prior art, so-called products after secondary recrystallization annealing (also referred to as finish annealing) are provided with grooves, or by irradiation marks with a laser or the like to subdivide magnetic domains, or after cold rolling or primary rolling. A method of forming grooves in a steel sheet after recrystallization annealing (also called primary annealing) is also performed. However, these methods use the so-called conventional forsterite (Mg ₂ S
The basis is to form a primary coating of i0 ₄ ).

However, with this method, it is difficult to reduce so-called iron loss as much as amorphous. The reason is,
Since the insulating primary coating called forsterite does not allow magnetic flux to pass through, it is considered to have an extra additive in terms of magnetic properties per unit weight of the entire steel sheet, and this primary coating is thick in order to obtain high magnetic flux density. Because it is so disadvantageous. From this point, recently, several methods of manufacturing a silicon steel sheet with little or no primary coating have been tried, but none of them is sufficient in terms of combination with the above-mentioned magnetic domain control, and from the viewpoint of economical efficiency. I have to say that there is a lot of room for improvement industrially.

[0005]

DISCLOSURE OF THE INVENTION The present invention has clarified such problems, and based on the technical knowledge shown in the following outline, formation of a solid substance containing forsterite as a main component called a primary coating is formed. Provided is a new method for producing a domain-oriented subdivided grain-oriented electrical steel sheet in order to obtain a grain-oriented electrical steel sheet with an extremely low iron loss as much as possible.

[0006]

The present invention was devised as an epoch-making means in order to solve the above problems. The outline is as follows. (1) Si: 1 to 7%
In the production of a grain-oriented electrical steel sheet having the basic steps of hot-rolling, cold-rolling, primary recrystallization annealing and secondary recrystallization annealing in molten steel containing an oxide in the steel sheet after primary recrystallization annealing. A method for producing a domain-divided unidirectional electromagnetic steel sheet, which comprises spraying the steel sheet surface, then rolling the steel sheet surface with a roll having protrusions, winding and then secondary recrystallization annealing.

(2) The maximum height of protrusions of the roll from the roll reference surface is 1 to 100 μm, the width of the protrusion of the protrusion in the roll circumferential direction is 2 to 400 μm, and the roll circumferential direction between the protrusions is the circumferential direction. Of 2 to 50 mm, and the longitudinal direction of the protrusions is 40 to 90 degrees with respect to the roll rotation direction. Generally, in a silicon steel sheet, after the primary annealing, the surface of the steel sheet is coated with a slurry of magnesia (MgO) dissolved in water using a coater roll,
A method is employed in which this is dried at a low temperature of around 350 ° C. and then brought to finish annealing. Of course, upon finish annealing, MgO reacts with Si or SiO ₂ in the steel to form forsterite. Even if the grooves are formed on the surface of the steel sheet in the step prior to the finish annealing to control the magnetic domains, the same result can be obtained.

Therefore, for the above reasons, the magnetic flux density cannot be improved and the iron loss cannot be decisively reduced. On the other hand, from the viewpoint of manufacturing, in finish annealing that needs to be performed at a high temperature, some sort of annealing separator is necessary also in the sense of preventing adhesion of steel sheets. Therefore, according to the present invention, MgO is not used, or a method of using other oxides such as alumina, which has a weak direct reactivity with Si or SiO ₂ such as alumina, as a finish annealing separator is used. It is a thing. As a result, it is possible to obtain a steel plate in which the primary coating of forsterite is basically not formed or only a very small amount is formed, and finally a steel plate with a very low surface roughness can be manufactured as a product. The knowledge that there is was obtained.

Another important component of the present invention is the method of applying the oxide to the steel sheet. In the prior art, MgO
Although a method of making an oxide into a slurry using water and applying it with a coater roll or the like is widely used, the method as it is cannot be used in the present invention. The reason is that it is better not to make forsterite basically in the present invention, so when the steel plate surface is activated and a large amount of water is present, rust occurs on the steel plate surface,
This is because foreign matter is subsequently formed by finish annealing, many foreign matter is generated on the surface after finish annealing, and reduction in roughness of the steel sheet surface is significantly hindered.

That is, the purpose of the present invention is not to achieve the effect of smoothing the surface of the steel sheet and reducing the iron loss by itself and reducing the iron loss by using the magnetic domain control together. Therefore, it is necessary to apply the oxide to the steel sheet dry or by the following method. At this time, the atmosphere is N ₂ , Ar,
It can be used in gases such as H ₂ . In addition, except for water, when dissolving in a solvent that does not cause rust on the steel plate, such as alcohol, an appropriate amount of water containing a rust inhibitor, or water as usual, 600 ° C later
Performing the above high temperature heating does not necessarily go against the gist of the present invention.

By the way, since oxides have almost no reactivity with the steel sheet at room temperature, simply sprinkling them from above is not sufficient because they are easily peeled off in the winding step for the final annealing in the next step. . Therefore, the following method was considered in the present invention. That is, before the primary annealed steel plate is wound as it is, or before it is wound again and before it is rewound, the oxide is first sprayed dry from the upper surface of the steel plate, and then a projection is formed on the surface at a certain pitch. This is a method in which the material is attached to a steel plate while being rolled down and wound up as it is.
Needless to say, the method of rolling with a roll secures the adhesiveness more than that of the case of merely spraying, but the purpose of the present invention is not limited to this.

First of all, it is more important to increase the reactivity of the oxide with the base iron in order to reduce the surface roughness after finish annealing and increase the iron loss by using the first oxide as an annealing separator. Therefore, it is necessary to make the oxide particles as small as possible for this purpose. Next, it is necessary to adhere the oxide to the steel sheet as much as possible so that the oxide powder does not peel off from the steel sheet during the next winding. The present invention has both the crushing effect and the adhesion improving effect. That is, in the present invention, a particularly important point is the effect of the roll with protrusions. It is natural that a groove is formed in the steel plate by this projection, and it remains in the product, resulting in a magnetic domain subdivision effect, but on the other hand, during the rolling reduction (compression rolling), this projection exists at a certain pitch. It was found that the so-called powder was tightened down, and the pulverizing effect of the oxide and the adhesiveness to the steel sheet were particularly good points.

That is, it has been found that this roll with protrusions is more effective than two birds with one stone. The following reasoning was attempted for the purpose of examining this effect. Considering the deformability as an aggregate of oxide particles as that of a kind of plastic body, it becomes as shown in FIG. In FIG. 1, the stress in the roll rotation direction is σ _w , the stress in the roll axis direction perpendicular to it is σ _L , and the stress in the direction perpendicular to the plate surface is σ _T. On the other hand, the equivalent stress σ _eq of the plastic body is expressed by equation (1).

Σ _eq = (1 / √2) √ (σ _L −σ _w ) ² + (σ _w −σ _T ) ² + (σ _T −σ _L ) ² (1) For plastic yield, this σ _eq is constant. Suppose this happens when the value σ ₀ is reached. When there is no protrusion on the roll as shown in FIG. 1 (a), σ _L ≈0 and σ _w ≈0 can be set, and the yield condition is expressed by equation (2). σ _eq = σ _T = σ ₀ (2) On the other hand, when the roll has a protrusion as shown in FIGS. 1 (b) and 1 (c), the roll rotation direction is constrained.
On the other hand, σ _L ≈0, but σ _w has the following significant values, and the yield condition at this time is as shown in equation (4).

[0015] _{ε w = λ {σ w -} (σ T + σ L) / 2} = 0 → σ w = σ T / 2 (3) σ eq = (1 / √2) √ (σ T 2/4 + σ T ^{_{2/4 + σ T 2 =}} (√3 / 2) σ T = σ 0 → σ T = 2 / √3σ 0 ≒ 1.15σ 0 (4) (2), as apparent from comparison (4) When the roll has a protrusion, the stress perpendicular to the plate surface is larger than when the roll has no protrusion, so a certain compressive strain (that is, the same σ _{eq of} (1)) is applied to the plastic body. If
The stress σ _{T, which} is perpendicular to the plate surface, is increased by adding protrusions to the roll.

When an oxide powder is sprinkled on a steel sheet for the purpose of increasing σ _{T and} the material is rolled down, the adhesion of the oxide to the steel sheet is improved, and since σ _w is 0 or more, the oxide content is 2
The shape is pushed from the direction, and the thickness of the oxide is secured. Further, the crushed state of the oxide particles becomes finer and the reactivity also increases. FIG. 2 is a graph showing the adhesion of oxides to a steel sheet and the iron loss characteristics of the product after finish annealing in an experiment for the steel sheet (sheet thickness 0.23 mm) of the components shown in Table 1.

[0017]

[Table 1]

A dry fine powder of alumina having an average particle size of 9 μm and a ratio of the standard deviation of the particle size to the average particle size (described later) of 25% was used to form rectangular protrusions (height: 30 μm, width: 5) with an average interval of 7 mm.
(0 μm) and a steel roll with a diameter of 300 mm and a steel roll of the same type without protrusions, after rolling with the same reduction amount (23%) with respect to the alumina powder, this steel sheet has a radius of curvature R =
Bending was carried out in a bending test of 150 mm (n = 5), and the ratio of the peeled surface area of the oxide powder and the iron loss value when this steel sheet was finished and annealed into a product were examined.

As shown in FIG. 2, when the roll was provided with protrusions, the powder did not peel off and the adhesion was good. Also, the iron loss characteristics of the product were good when the groove was formed on the roll, because a stable and low value was obtained. In order to improve the adhesion of the oxide to the base iron in the present invention, it is preferable to activate the surface by performing activation treatment such as pickling after the primary annealing.

The activation method of this kind is, of course, other than pickling, use of other chemicals, mechanical methods such as brush, shot blasting, high water pressure, electrical methods such as static electricity and magnetism, There are various physical methods such as sound waves. In the present invention, in order to bring the oxide powder into close contact with the steel sheet, reduction was carried out by means of a roll with protrusions, but it is also possible to use the principle of the electrostatic coating method as an auxiliary means in combination without changing the essence of the present invention. In some cases, it is rather preferable.

Next, the constraints on the shape of the roll protrusions will be described. When it is less than 1 μm, the constraint of the deformation of the plastic body of the powder in the roll rotation direction is weak and the effect is not sufficient.
On the other hand, if it exceeds 100 μm, the normal amount of spraying (spraying thickness 10 to 10
At about 50 μm), the contact with the steel plate body is too large as compared with the powder restraint, and the tightening of the powder is not sufficiently effective. If the width of the protrusion is less than 2 μm, the powder cannot be sufficiently restrained. On the other hand, if it exceeds 400 μm, too much powder is applied, resulting in an imbalance in the thickness of the powder after reduction (rolling and pressing), and eventually variations in the magnetism of the product. Here, the width of the protrusion is the roll surface (bottom surface) of the protrusion.
Refers to the width of a part.

If the average interval between the protrusions is less than 2 mm, too much powder is applied to the powder to cause an imbalance in the powder thickness, resulting in variations in the magnetism of the product. On the other hand, 50 mm
If it exceeds the above range, the constraint of the deformation of the powder plastic body in the roll rotation direction is weak, and the sufficient effect of the present invention cannot be obtained. If the longitudinal direction of the protrusion is less than 45 ° with respect to the roll rotation direction, the magnetic domain control cannot be sufficiently exerted, and improvement of magnetism cannot be expected.
Regarding the shape of the protrusions, it is not always necessary to regularly attach the same shape to one roll, and the pitch may not be constant.

This technical significance is very great. That is, if the oxide is simply pressure-bonded to the steel plate and simultaneously crushed, the rolling load may be increased, but this also reduces the thickness of the pressure-bonding. That is, the strain becomes too large, and it is difficult to obtain a predetermined required amount (thickness) of the oxide, and the oxide itself is crushed more than necessary to obtain a predetermined characteristic in the subsequent finish annealing step. Can be difficult. Also for the purpose of preventing these, rolling with an oxide steel sheet by a roll with protrusions is an excellent method.

The projections do not necessarily have to be continuously connected to the entire width of the roll. The so-called broken line shape, one-dot chain line shape, multi-dot chain line shape, etc. do not impair the object of the present invention.
It is determined only by the ease of roll manufacturing, and usually the same protrusions are regularly attached. Further, in addition to this protrusion, an unspecified pattern for the purpose of tightening the powder, for example, using a checkered pattern as an auxiliary is also consistent with the purpose of the present invention, but in this case, it does not disturb the magnetic domain control. It needs to be light. In the present invention, the use of a roll with protrusions on the upper surface of the steel sheet and oxide powder are considered in principle, but of course the application of oxide from the lower surface does not hinder this.

In particular, the combination of electrostatic coating is extremely effective. Also, of course, the use of opposite rolls or backup rolls as a pair of raised rolls is in accord with the purpose of the present invention. Further, it is also effective to provide a filter (gate) for leveling the oxide powder on the steel plate to a certain height in front of the roll with protrusions. further,
Before spraying the oxide itself on the steel plate 600-1000
It is extremely useful to heat in a non-oxidizing atmosphere (N ₂ , Ar, H ₂ gas, etc.) in the range of ° C. The reason is that the oxide powder is activated to increase the adhesiveness to the steel sheet, and it is easy to form a groove neatly when making a groove on the steel sheet with a roll with protrusions, and it is possible to cool the vicinity of this groove during finish annealing in the subsequent process. This is because it is effective in making it difficult to form a group of fine particles due to inter-strain and improving the magnetic characteristics of the product. In that sense, it is also useful to heat the steel sheet at the above temperature immediately before or during rolling with a roll having protrusions. Here, 600 ° C. is the lower limit temperature at which the oxide adheres to the steel sheet and does not form fine particle groups in the vicinity of the groove later. On the other hand, above 1000 ° C., the oxides rather agglomerate and abnormal particles near the groove. Will be more likely to occur.

Now, there is an optimum range for the average particle size of the oxide dispersed in the present invention. The smaller the size, the better the reactivity with the surface and the roll press-bonding tightening property, but if the size is too small, agglomeration tends to occur, and the lower limit is preferably 0.5 μm. On the other hand, if it is too large, it does not adhere to the steel sheet first, and it is difficult to be crushed even by rolling, resulting in deterioration of adhesion and reactivity, so the upper limit is 10
It becomes 0 μm. It is preferably 8 to 30 μm. Further, variations in oxide particle size are also important. The following standard deviation: σ _n = [{ΣX ² − (ΣX) ² / n)} /
n] ^1/2 where X is the particle size, n is the ratio of the standard deviation of the particle size expressed by the number of particles to the average particle size, and is 100.
If the ratio multiplied by exceeds 70%, it is difficult to uniformly grind during rolling, the reactivity with the oxide steel sheet is poor, and especially for the purpose of regularly forming grooves with protrusions, the groove depth Is difficult to be uniform, and the magnetism varies depending on the location. Usually, unless you mix particles with different sizes,
This value can be controlled to 20% or less.

Further, the amount of rolling and pressure bonding with a roll is also important. As a matter of course, when the reduction amount is extremely small, the powder cannot be brought into close contact with the steel sheet, which is the object of the present invention, and a reduction amount of at least 3% is necessary. Further, in order to sufficiently form the groove by the projection on the steel plate, preferably 10% is necessary. On the other hand, if it exceeds 90%, the powder will be pressed and aggregated.

Further, if the groove formed by the projection on the steel sheet is too deep, the magnetism rather deteriorates depending on the shape of the projection, so 70% or less is preferable. The definition of the reduction amount (%) is as follows: the thickness (T ₀ ) of the oxide powder before it enters the roll and the thickness (T
₁ ) is how much is reduced, and 100 × (T ₀ −
It is represented by T ₁ ) / T ₀ . Next, the shape of the protrusion attached to the roll will be described. This has a sectional shape perpendicular to the longitudinal direction of the protrusion, but any of the following may be used. Squares, rectangles, triangles, trapezoids, parts of circles, parts of ellipses, parts of parabolas, spindles, parts of polygons, and combinations thereof.

Further, a shape obtained by correcting some of these parts,
For example, a trapezoidal shape, a rectangular shape, a triangular shape, or the like having a rounded corner portion with a certain curvature does not change the essence of the present invention, and the point is that the basic principle of the present invention is industrially applied including the tool life. The method of facilitation is consistent with the purpose of the invention. Further, although the material of the roll is not specified, any material may be used as long as it is hard and has appropriate toughness. For example,
Steel, non-ferrous metal, ceramics, diamond, etc. can be considered as examples, but the manufacturing method may be a forging method, a casting method, or a powder metallurgy method. Further, the inside is steel and only the outside is made of non-steel as described above, or only the surface is C
It is also useful to treat with a special heat resistant and wear resistant hard material such as VD and PVD. Further, it can be said that it is preferable in terms of cost to manufacture only the protrusions on the roll main body with another substance and to attach and combine them, thereby reducing the basic unit.

Next, the types of oxides will be described. In short, as mentioned above, it is important not to generate a large amount of forsterite (Mg ₂ SiO ₄ ) by reacting with Si, SiO _2, etc. in the steel, and it is possible to satisfy it and withstand the high temperature of finish annealing. Any oxide with a high melting point may be used. Be, B, Al, Si, P, Ca, Se, Ti,
V, Cr, Mn, Co, Ni, Cu, Zn, Ga, G
e, Sr, Y, Hf, Zr, Nb, Mo, Te, Ba,
Sb, La, Ce, Ta, W, Bi, Pb, Na and the like.

These oxides can also be used in combination with one another. Among them, it can be said that Al, B, W, etc., which are stable at high temperature, harmless to magnetism even if they melt into steel, and are inexpensive, are industrially easy to use. As will be described later, if forsterite is 0.3 μm or less, a target low iron loss can be sufficiently obtained on the premise of magnetic domain control by groove formation in the steel sheet according to the method of the present invention. It does not change the essence of the present invention to mix the oxide of Mg if it is a part of the oxide.

In the present invention, unlike conventional silicon steel sheets, forsterite is basically not generated, so that tension is applied to improve iron loss after finish annealing, and coating is particularly required to secure insulation. Various methods are conceivable for this, but the present method of applying a coating such as phosphoric acid or chromic acid-based coating and firing, or repeating this,
A method of applying an oxide, such as alumina, spinel, or cordierite, having a thermal expansion coefficient lower than that of iron by the Zolgel method and firing, or by directly applying an oxide or a nitride to the surface by CVD, PVD, or the like. Any method, such as a method, can be used as long as it provides tension and insulation to steel.

The secondary recrystallization of grain-oriented silicon steel sheet is GO.
It is important to grow grains of {110} [001] orientation called SS orientation during secondary recrystallization annealing (also called finish annealing). This is a method for coarsely recrystallizing only certain specific grains in the primary recrystallization annealing (also called primary annealing). At this time, an inhibitor (Inhibito) is used.
It is well known in the art that it is technically necessary to make fine precipitates called r) such as AlN before finish annealing.

Then, nitrogen necessary for this purpose is added during steel melting, after primary annealing, or during other steps. In that case, it was also found that the method of adding nitrogen after the primary annealing is the optimum method of adding nitrogen for the purpose of the present invention. If nitrogen is added during or immediately after the primary anneal, the nitriding reaction facility is usually installed inside or close to a part of the primary anneal facility that also functions for decarburization, and after or after the primary anneal. The method of causing the nitriding reaction is also effective.

In the case of steel having a sufficiently low carbon content at the time of steel melting, it is more important than the decarburizing function to change the oxide layer of the surface layer after the primary annealing so as to make it advantageous for the coating reaction.
By the way, in the present invention, secondary recrystallization annealing is performed, and heat flattening annealing and insulating film coating are performed as necessary. In the present invention, the average depth of the maximum part from the base metal surface, which will introduce strain into the steel sheet surface by the roll after primary annealing, is 2 to 80 μm.
It is desirable to regularly provide the grooves. This is because the grooves can make the magnetic domains of the product finer and contribute to the reduction of iron loss.

However, with this alone, the extremely low iron loss aimed at by the present invention cannot be obtained. The most important technical requirement of the present invention is that it does not form a forsterite coating. It was found that even if formed in this way, when the average thickness of the primary film containing forsterite as a main component is 0.3 μm or less, the magnetic properties are remarkably improved in combination with the above. The reason for this is not necessarily understood, but if this primary coating is thick, it obstructs the flow of the magnetic flux of the steel sheet, especially if the coating has many irregularities, or if the spinel (M
It can be easily imagined that this tendency is large when there are many oxides such as gO.Al ₂ O ₃ ).

Therefore, if the primary coating on the surface is reduced as much as possible to be thin or completely eliminated, and regular grooves are formed instead, the magnetic flux will flow regularly and smoothly. As a result, iron loss can be sufficiently reduced. As will be described later, the depth and pitch of the groove are naturally limited.

[0038]

[Table 2]

A grain-oriented electrical steel sheet having the chemical composition shown in Table 2 (the N content of R1 is the value after primary annealing and nitriding) is hot-rolled, hot-rolled and annealed, and then cold-rolled to 0.15 mm. Done,
Dry type alumina (Al ₂ O ₃ ) powder on steel plate, Mg
Rolled rolls with protrusions (maximum protrusion height 25 μm, width 30 μm, pitch 45 mm) after spraying various additives to O powder, and those obtained by dissolving MgO powder in water to form a slurry and using a coater roll. FIG. 3 shows the iron loss of the sample which was subjected to finish annealing and further coated with an insulating coating having tension.

From this, it is apparent that the one coated with alumina has the lowest iron loss, while the one using MgO shows a reduction (improvement) in the iron loss as the thickness of the primary coating becomes smaller, and particularly It can be seen that it is remarkable at 3 μm or less. Especially dry type is excellent. In the present invention, forsterite is basically unnecessary, and it is preferable that it is not. However, even if it is mixed as a part of the oxide powder, if it is forsterite of such a degree, there is no harm to the object of the present invention.

Next, when significantly adding Al in the case of performing secondary recrystallization, AlN or S is used as one of the inhibitors.
It has also been found that i ₃ N ₄ is used, but the method of nitriding during or after the primary annealing as one of the methods of the present invention is more preferable for the purpose of the present invention. This is for the following reason.
Unlike the case where a large amount of nitrogen is added during steel melting, it is easier to control the optimum amount of AlN and Si ₃ N ₄ by nitriding later, and during secondary recrystallization annealing, it is possible to perform primary recrystallization such as forsterite as in the present invention. It is considered that the optimum nitrogen amount can be easily secured by controlling the nitrogen partial pressure (P _N2 ) in the atmosphere even if the film becomes thin or disappears.

Next, as described later, in order to reduce or eliminate the primary coating film during finish annealing as much as possible, in the present invention, an oxide other than MgO, for example, alumina is dry-coated on the surface of the steel sheet after primary annealing. It has been found that this purpose can be sufficiently achieved, but on the other hand, even if special chloride or sulfide is mixed in ordinary magnesia (MgO) powder and sprayed, the average primary coating thickness of 3 μm or less can be obtained. It is also known as knowledge that it is possible.

Among them, calcium chloride (Ca
Cl ₂ ) and potassium sulfide (K ₂ S) are particularly effective.
In addition to MgO, TiO ₂ and antimony-based oxides (Sb ₂ (SO ₄ ) ₃ ), boron-based oxides (Na ₂ (BO ₄ ) ₃ ), strontium-barium-based oxides, carbon -Nitride-based materials are added to facilitate the reaction. However, since the effects of these additives are exerted in the present invention as well, the addition does not change the essence of the present invention. Now, a method for manufacturing a silicon steel sheet will be described next.

As described above, the silicon steel sheet according to the present invention is S
In addition to i, if necessary, Al is contained, and if Si ₃ N ₄ or AlN and S in the steel are large, MnS is used as a main inhibitor, and P, Sn, and Se, Sb, Cu, B, Nb, Ti, V, N
The addition of other additive elements such as i, Mo, Cr, Bi, W, and Hf to improve the magnetic characteristics does not change the basics of the present invention. P, Bi, etc. are also effective in improving the magnetic flux density.

By the way, AlN or Si ₃ N ₄ , Mn
Steel containing S as an inhibitor is known, and the technique of the present invention can be applied to any of the cases. However, the following production method is most suitable for further exerting the characteristics of the present invention. That is, in a steel containing 1 to 7% of Si, if necessary, Al is contained in an amount of 0.1% or less when the steel is melted, and N is directly applied to the steel sheet during or after decarburization annealing during primary annealing after cold rolling in the silicon steel sheet manufacturing process. This is a method characterized in that N is contained in 30 ppm to 600 ppm steel before secondary recrystallization annealing by a method of forcibly adding N to steel through a nitriding reaction.

In the present invention, Si is a source of
A minimum of 1% is required for the formation of rusterite. one
On the other hand, if it exceeds 7%, the workability is extremely deteriorated and it is suitable for industrial production.
I don't. Al is effective in forming an AlN inhibitor.
However, if it exceeds 0.1%, Al ₂O₃The amount of production increases
Impairs the cleanliness of sound steel, which in turn adversely affects magnetic properties
Bring

N is indispensable for forming Si ₃ N ₄ and AlN inhibitor, and when AlN is used as an inhibitor, in the present invention, after the primary annealing, that is, before the start of secondary recrystallization of finish annealing. A minimum of 30 ppm is required. On the other hand, when Al is intentionally used, 60 ppm or more is necessary to secure the amount of AlN. However, 60
If it exceeds 0 ppm, Al and Si are excessively eaten, which is not preferable. This is not the case when AlN is not used.

P is useful in the invention for increasing the magnetic flux density. When the steel is melted, if it is less than 0.04%, the effect of increasing the magnetic flux density is small, while if it exceeds 0.20%, the brittleness becomes large and cold rolling is difficult. In the present invention, Sn and Cu are remarkably effective in reducing iron loss when coexisting with P. If the total content of one or more of them is less than 0.02%, there is no such effect, while if over 0.20%, the primary coating is sufficient. Can not.

When S is positively used, at least 0.01% S is necessary for effectively using MnS as an inhibitor. On the other hand, if it exceeds 0.05%, aggregation is not preferable. In the present invention, other elements are not particularly characteristic as compared with the conventional steel, but it is preferable to restrict them as follows. C must be sufficiently low during steel melting or sufficiently low during decarburization annealing of primary annealing, and 0.03% or less is preferable at the start of secondary recrystallization annealing.

If Mn is less than 0.5%, it reacts with S and becomes M.
Form nS inhibitors. If it is 0.15% or less, it is preferable for further improving the magnetic flux density. O is 0.05 after melting steel
% Or less is preferable in terms of cleanliness without producing too much Al ₂ O ₃ . Next, the production method of the present invention other than the chemical components will be described.

Steel is tapped in a converter or an electric furnace, and if necessary, a refining process is added to adjust the composition of the molten steel, which is used for continuous casting, ingot slabbing or hot rolling. A thin slab continuous casting method or the like is used to form a slab having a thickness of 30 to 400 mm (50 mm or less in the thin slab continuous casting method). Here, 30 mm is the lower limit of productivity, and 400 mm is the upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. Further, 50 mm is the upper limit for suppressing the generation of coarse particles due to the low cooling rate.

The slab is reheated to 1000 ° C. to 1400 ° C. by gas heating, electric heating, etc., and then hot rolled to obtain a hot coil having a thickness of 10 mm or less.
Here, 1000 ° C. is the lower limit of AlN melting,
C is the upper limit of surface roughness and material deterioration. Further, 10 mm is an upper limit for obtaining a cold speed at which an appropriate precipitate is formed. In addition,
In the thin slab continuous casting method, it is possible to directly form a coil, and for that purpose, 10 mm or less is preferable. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve magnetism. Here, 800 ° C. is the lower limit of remelting of AlN, and 1250 ° C.
Is the upper limit for preventing AlN coarsening.

After this treatment step, the hot coil is directly or batch-pickled and then cold-rolled. Cold rolling is performed at a rolling reduction of 60 to 95%, but 60% is the limit of recrystallization in the present invention, and preferably 70% or more by primary annealing and increasing {111} [112] oriented grains. Is the lower limit for promoting the generation of GOSS oriented grains during the secondary recrystallization annealing,
On the other hand, if the content exceeds 95%, secondary recrystallization annealing causes GOSS-oriented grains, which are called swinging GOSS grains, to rotate in the plane of the plate to produce grains unfavorable to the magnetic properties.

The above is the case of manufacturing by the so-called single cold rolling method. However, in the case of performing cold rolling-annealing-cold rolling called the double cold rolling method, the first rolling reduction is 10 to 80%, The second rolling reduction is 50 to 95%. Here, 10% is the minimum reduction ratio necessary for recrystallization, 80% and 95% are the upper limit reduction ratios for producing proper GOSS-oriented grains during secondary recrystallization, respectively, and 50% in the double cold rolling method. Is the lower limit of the reduction ratio that appropriately leaves the {111} [112] oriented grains during the primary annealing.

It is also commonly called "interpass aging", and it is effective to improve the magnetic properties by heating the steel sheet in the range of 100 to 400 ° C by an appropriate method during the cold rolling. 10
Below 0 ℃, there is no effect of aging, while at 400 ℃
If it exceeds the limit, dislocations will be recovered. After that, primary annealing is performed, and at this time, nitriding is performed if necessary. Both the single cold rolling method and the double cold rolling method perform primary annealing, but it is effective to perform decarburization by this annealing. As described above, C is not preferable for the growth of secondary recrystallized grains, and if it remains as an impurity, it causes deterioration of iron loss. In addition, not only shortening the decarburization process if C is lowered during the melting of steel {11
1} [112] oriented grains are also increased, which is preferable. By setting an appropriate dew point in this decarburization annealing step, an oxide layer necessary for subsequent primary film formation is secured.

The primary annealing temperature is preferably 700 to 950 ° C. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and
50 ° C. is an upper limit temperature that suppresses the generation of coarse particles. Furthermore, in the present invention in which N of AlN or Si ₃ N ₄ inhibitor is forcibly added by the nitriding method during this primary annealing, ammonia (NH ₃ ) is continuously added during or immediately after the above primary annealing.
Nitriding is performed by a nitriding method.

The temperature of the nitriding method in this case is 600 to 950.
℃ is good. Here, 600 ° C. is the lower limit for causing the nitriding reaction, while 950 ° C. is the upper limit for suppressing the generation of coarse particles. In the present invention, nitriding is preferably performed after the primary recrystallization annealing, but industrially, a partition is provided on the rear surface of the same furnace and the atmosphere is slightly changed as necessary, and NH ₃ gas is passed or a nearby facility is installed. Therefore, it is often nitrided in parallel with primary recrystallization. At this time, as described above, the lower the partial pressure of N ₂ is, the larger the amount of nitriding is, and the partial pressure ratio P _N2 / P _H2 of nitrogen and oxygen is preferably 0.5 or less. The step of spraying the oxide on the surface of the steel sheet after the primary annealing and press-bonding it with a roll having protrusions is particularly important in the present invention. This oxide may be any of the above-mentioned substances other than MgO, but some M
If gO is used as a mixture, the following method is preferable. In this case, in particular, it is necessary to make the average thickness of the primary coating after secondary recrystallization annealing 3 μm or less as described above. For this purpose, in magnesia (MgO), with respect to 100 parts by weight of MgO,
Li, K, Na, Ba, Ca, Mg, Zn,
0.5 to 20 parts by weight of one or more sulfides such as Fe, Zr, Sn, Sr and Al and / or one selected from carbonates, nitrates and chlorides of these elements Alternatively, it is preferable to apply an annealing separator in which 0.5 to 20 parts by weight of two or more kinds are added and chloride, sulfide or oxide is added.

In this case, for example, calcium chloride (CaCl ₂ ) among chlorides and potassium sulfide (K ₂ ) among sulfides.
S) is the representative. The amount of this addition is 0.5-20%
(Weight ratio when the weight of MgO is 100) is preferable. If it is less than 0.5%, there is no effect of thinning the primary coating,
On the other hand, if it exceeds 20%, the reactivity is deteriorated and the secondary recrystallization is not sufficiently performed.

On the other hand, a trace amount of an appropriate compound may be added for the purpose of facilitating the melting of the MgO powder during the subsequent secondary recrystallization annealing and promoting the forsterite formation reaction. When MgO is used, TiO ₂ , Sb ₂ (SO ₄ ) for forming forsterite is used.
It is useful to add ₃ or Na ₂ B ₄ O ₇ .

However, for the purpose of the present invention, it is possible to manufacture a grain-oriented silicon steel sheet having a surface in which other oxides are thinner or almost mirror-like without using MgO. It is possible to further reduce iron loss in combination with manufacturing conditions. Next, the groove formation will be described. The method of forming the groove is as described above, but more preferably, the average domain depth of the groove is 2 μm or more, the effect of subdividing the magnetic domain becomes large, while if it exceeds 80 μm, the depth is too deep to ensure a smooth flow of magnetic flux. From the standpoint of controlling the magnetic domain by the groove, 2 to 80 μm is preferable because it can be prevented and the iron loss is worsened. The grooves should be regularly arranged. This is because the magnetic domain is subdivided regularly.

Usually, it is preferable to engrave at a substantially constant pitch having an angle of 45 degrees to a right angle with respect to the longitudinal direction of the steel sheet. If it is less than 45 degrees, the direction of magnetic domain subdivision does not match the crystallographic orientation preferred for magnetism. The groove pitch is preferably 2 to 50 mm. The reason for this is as described above, but if it is less than 2 mm, the domain division will be too advanced.
The 0 ° domain increases, and the iron loss and magnetostriction are bad. On the other hand, if it exceeds 50 mm, there is no effect of domain division.

In the present invention, the secondary recrystallization annealing is preferably carried out at the highest temperature reached of 1100 to 1300 ° C.
1100 ° C. is the lower limit temperature at which secondary recrystallization is performed,
On the other hand, if the temperature exceeds 1300 ° C., the crystal grains become too coarse, and the iron loss is deteriorated. The important points in this secondary recrystallization annealing are as follows. In the present invention, there is no primary coating containing forsterite as a main component, or even when MgO is used, it is extremely reduced or eliminated, so that a nitrogen-based inhibitor (AlN, Si ₃ N 2) is added to secondary recrystallization during annealing. ₍₄ etc.) is mainly used, N is included in the finish annealing, and the inhibitor of that compound tends to escape, so the nitrogen partial pressure (P _N2 ) in the atmosphere gas of the finish annealing is set to 30% or more. This can prevent this, and stable secondary recrystallization can be obtained.

On the other hand, when MnS or another compound is used in addition to the N-type inhibitor, the secondary recrystallization tends to be stable even without being restricted by this restriction.
After the secondary recrystallization is completed, it is better to reduce the N ₂ partial pressure to 0 or to increase the H ₂ partial pressure to 100% before or after reaching the maximum temperature for purification. Further, if the rate of temperature rise in the secondary recrystallization annealing is too high, the inhibitor easily escapes before sufficient secondary recrystallization occurs. Therefore, it is rather preferable to keep the rate of temperature rise below 50 ° C. for stable magnetic properties. can get. Note that, as described above, the nitriding method in which nitrogen is additionally added from the atmosphere or the like may be performed at a relatively previous stage during the secondary recrystallization annealing.

The above is an important part of the method for producing a silicon steel sheet according to the present invention, but industrially, the steel sheet after secondary recrystallization is insulated with an organic or inorganic substance for the purpose of further improving the insulation characteristics and magnetic characteristics. It is particularly important to apply a high-strength coating having a coating (such as roll coating or Zolgel method) in combination with heat treatment or the like. The reason for this is that in the present invention, there is basically no primary coating having high tensile properties such as forsterite, or even if there is, it is extremely small,
This is because it is effective to apply an insulating coating having high tensile strength to complement this.

Before and after the application, heat treatment for heat flattening or heat treatment for improving the iron loss and the like by facilitating the high tension coating to be closely applied to the steel sheet and the like can be performed as needed. It is also preferable from the point of the present invention.

[0066]

EXAMPLES Steels having chemical compositions shown in Tables 3, 4, 5, 6 and 7 were melted in a converter and produced under the conditions shown in Tables 3, 4, 5, 6 and 7. .

[0067]

[Table 3]

[0068]

[Table 4]

[0069]

[Table 5]

[0070]

[Table 6]

[0071]

[Table 7]

The hot-rolled sheet was partially annealed under the conditions of 11
After being carried out at 20 ° C. for 30 seconds, it was rapidly cooled. Aging between passes during cold rolling was performed except for B-5, but the condition was 25.
It is 0 ° C. Although a part of the nitriding subsequent to the primary recrystallization annealing was performed, it was performed by making the atmosphere dry with the same gas composition in the inner part of the furnace where the partition was provided in the same furnace and flowing a certain amount of NH ₃ gas. It is a thing.

The amount of nitriding after the primary annealing (the amount of nitrogen in the steel after the primary annealing) is shown in the same table. Further, this steel sheet was sprayed with an oxide powder by the method of the present invention, various shapes and conditions were changed, and pressure-bonded with a roll having protrusions. A-20, B-
All were performed dry except 5 and B-7. For B-6, the oxide was rolled down (compression rolling) in an N ₂ gas atmosphere. In addition, as for B-7, a small amount of an organic solvent was included in an oxide and pressure-bonded.

On the other hand, for B-5, a small amount of water containing a rust preventive was included in the oxide and pressure-bonded. Also, A-2 and A-4 are oxide powders in an atmosphere of N ₂ 70% + H ₂ 30% 900
After heating to ℃, it was sprayed on the steel plate. In A-4 and A-19, immediately before rolling the steel sheet with a roll having protrusions, the steel sheet was rolled at 800 ° C. in a Ar atmosphere with a burner and then rolled.

A-20 was prepared by dissolving an oxide in water to form a slurry, coating the steel sheet on the upper and lower surfaces with a normal coater roll, and sealing the steel sheet in an atmosphere of N ₂ 50% + H ₂ 50%. After heating to 820 ° C., it was rolled by a roll with protrusions. In addition, the apex of the triangle of the protrusion of A-1, A
Both vertices of the -4 trapezoid are rounded with a large radius of curvature of 5 to 10 mm.

A-19 and A-20 are steel rolls with diamond and powder metal projections. Further, the pitch of the protrusions indicates the average distance between the protrusions, but for B-1, the pitches of 5 mm and 15 mm are alternately provided and expressed as the average. In addition, B-1, -2
Also used the electrostatic coating method to apply the oxide powder from the lower surface of the steel sheet. Then, after winding, secondary recrystallization annealing (finish annealing) was performed while changing the average temperature rising rate from 800 ° C. to the highest reached temperature and the atmosphere gas composition in various ways.

Here, the maximum arrival speed is 12000 ° C. After reaching the maximum temperature, the atmosphere gas is set to 100% H ₂
Switched to. Furthermore, various coatings were applied to produce a high-strength coating that provides tension and insulation, and heated for firing. Then, the plate was removed, and strain relief annealing was performed at 850 C for 4 hours (N ₂ 90-H ₂ 10, Dry), and a magnetic measurement test was performed. The results are shown in Tables 3, 4, 5, 6, and 7.

The magnetic measurement is SST of a single plate of 60 × 300 mm.
Measured by the test method, magnetic flux density of B ₈ (800 A / m), unit is Tesla and W _17/50 (iron loss at 1.7 Tesla at 50 Hz, unit is watt / kg), W _13/15 (50 Hz
The iron loss at 1.3 Tesla) was measured. Now, as shown in Tables 3, 4, 5, 6 and 7, the products within the scope of the present invention have excellent roughness, high magnetic flux density, low iron loss, and are sufficiently low. You can see that it is within the target range.

[0079]

As described above, according to the present invention, it is possible to obtain an ultra-low iron loss grain oriented electrical steel sheet.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a roll with protrusions and an explanatory diagram of stress conditions of a steel plate.

FIG. 2 is a diagram showing adhesion and iron loss characteristics of oxides according to examples of the present invention.

FIG. 3 is a diagram showing a relationship between an average thickness of a primary coating and iron loss.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Yamazaki 1-1 Tobahata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture Inside the Yawata Works, Nippon Steel Corporation (72) Inventor Katsuro Kuroki Tobata, Tobata-ku, Kitakyushu, Fukuoka No. 1 No. 1 within the Yawata Works, Nippon Steel Co., Ltd. (72) Inventor Isao Iwanaga No. 1-1 Tobata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture Within the Yawata Works, Nippon Steel Co., Ltd.

Claims (7)

[Claims] 1. In the production of a grain-oriented electrical steel sheet, which comprises smelting steel containing Si: 1 to 7%, hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing being the basic steps, Disperse the oxide on the steel sheet surface after primary recrystallization annealing, then roll down the steel sheet surface with a roll with protrusions, and after winding, carry out secondary recrystallization annealing. Chemical unidirectional electrical steel sheet manufacturing method. 2. The maximum height of protrusion of the roll from the roll reference surface is 1 to 100 μm, the width of the protrusion of the protrusion in the roll circumferential direction is 2 to 400 μm, and The method for producing a magnetic domain subdivided unidirectional electrical steel sheet according to claim 1, wherein the average interval is 2 to 50 mm, and the longitudinal direction of the protrusions is 40 to 90 degrees with respect to the roll rotation direction. 3. The method for producing a magnetic domain refined unidirectional electrical steel sheet according to claim 1, wherein the reduction rate of the oxide is 3 to 90%. 4. Alumina (Al
_The method for producing a magnetic domain refined grain-oriented electrical steel sheet according to claim 1, 2 or 3, wherein ₂ O ₃ ) is used. 5. The average particle diameter of the oxide particles is 0.5 to
The method for producing a magnetic domain subdivided grain-oriented electrical steel sheet according to claim 1, 2, 3 or 4, wherein the ratio of the standard deviation of the grain diameter to the average grain diameter is 100% or less and 70% or less. . 6. The method of spraying the oxide on a steel sheet, after cold rolling and before spraying on the steel sheet, the steel sheet is pickled or washed with an alkaline solution, or shot blasting, brush roll,
The magnetic domain subdivided unidirectional electrical steel sheet according to claim 1, 2, 3, 4 or 5, which is sprayed after surface grinding with high pressure water or ultrasonic waves, or after being charged with an oxide or magnetized and then sprayed on the surface of the steel sheet. Manufacturing method. 7. The oxide before spraying is 600-1000.
The method for producing a magnetic domain subdivided grain-oriented electrical steel sheet according to claim 1, 2, 3, 4, 5 or 6, which comprises heating to ° C.